A reactor is one of components of a circuit that performs an operation of increasing or reducing a voltage. For example, Patent Literature (PTL) 1 discloses a reactor included in a converter mounted in a vehicle, such as a hybrid vehicle. The reactor includes, for example, a coil, a ring-shaped magnetic core, a case, and sealing resin (secondary resin part). The coil includes a pair of coil elements that are arranged next to each other. The magnetic core includes a pair of pillar-shaped inner core portions (coil winding portions) that are inserted through the respective coil elements, and outer core portions (end cores) that connect the inner core portions, which are arranged parallel to each other, to form a closed magnetic circuit. The case houses an assembly of the coil and the magnetic core, and is filled with the sealing resin. According to PTL 1, the outer peripheral surface of each coil element, which has rectangular end faces, is covered with resin so that each coil element is formed as an independent body. The coil elements are connected to each other at one end thereof with a connecting conductor to form a single coil.
When the coil receives electricity and generates heat, the loss of the reactor increases owing to the generated heat. Therefore, in general, the reactor is used while being fixed to a cooling base so that the coil can be cooled. An operation of measuring the temperature of the coil and controlling a current applied to the coil in accordance with the temperature has also been studied. According to PTL 1, attachment grooves for receiving a temperature sensor are formed in surfaces of the bodies that oppose each other (opposing surfaces). The bodies are disposed near each other so that a columnar hole in which the temperature sensor can be inserted is formed by the attachment grooves. The attachment grooves extend in a direction orthogonal to both the direction in which the coil elements are arranged next to each other and an axial direction of the coil elements. The attachment grooves are formed so as to extend linearly over the entire length of the respective opposing surfaces from an edge at the bottom surface side of the case to the other edge (opposite edge) at the open side of the case.